Encrypt XML with X509 certificate

Question

I encrypt XML document with X509 certificate, I use this example http://msdn.microsoft.com/en-us/library/ms229744.aspx
<EncryptedData Type="http://www.w3.org/2001/04/xmlenc#Element" xmlns="http://www.w3.org/2001/04/xmlenc#">
<EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes256-cbc"/>
<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
<EncryptedKey xmlns="http://www.w3.org/2001/04/xmlenc#">
<EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-1_5"/>
<KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
<X509Data>
<X509Certificate>
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
</X509Certificate>
</X509Data>
</KeyInfo>
<CipherData>
<CipherValue>
</CipherValue>
</CipherData>
</EncryptedKey>
</KeyInfo>
<CipherData>
<CipherValue>
</CipherValue>
</CipherData>
</EncryptedData>
The encrypt XML consit element <X509Certificate>, I don't know what kind of cert info is in this element. In <X509Certificate> are public key, private key or what certificate info?
Because if I want decrypt I use :
// Create a new EncryptedXml object.
EncryptedXml exml = new EncryptedXml(Doc);
// Decrypt the XML document.
exml.DecryptDocument();
I don't must specify X509 certificate to decrypt XML file. How can work method  DecryptDocument()?

Answer 1

I wonder if the problem here is that <X509Data><X509Certificate> ... </X509Certificate><X509Data> includes a binary copy of the certificate WITHOUT the private key. (It wouldn't make any sense to include the private key...anyone could
decode it.) The Decrypt method is looking at the enclosed certificate and not finding a private key.
I think somehow Encrypt has to create an X509ThumbprintKeyIdentifierClause instead, but I haven't figured out how yet.